Best Option to Pursue

[moki75]

Looking for some advice

My father (a Belgian National) who essentially lived most of his childhood and adult life in a former British colony (Southern Rhodesia) has moved over to the UK with my mother (a British Citizen) over 6 years ago. They have been married in excess of 40 years.

I'm trying to find the best route for him to apply for residency status with a view to gaining British Citizenship.

He is elderly and no longer works but my mother and him are self sufficient and have got by on their savings. I can also add that I do have permanent residency status, have been married to a British citizen for over 6 years and we have two British born children (his grandchildren).

What is the best route for him to apply for residency?
I was initially thinking EEA PR application, but he has not taken private medical insurance out and not sure if this will disqualify him for making an application via that route (I wasn't aware of this as a requirement until I looked at the form which I was completing based on an individual who has been self sufficient). I guess I'm thinking what route is most likely to be the most successful

Please advise.
Many thanks.